Method for forming a composite elastic material

ABSTRACT

A method for forming a composite elastic material. An elastic member having at least one elastic strand is fed onto a rotating forming structure exhibiting a multiplicity of apertures therein. The elastic member has a surface facing the forming structure and another surface facing away from the forming structure. A thermoplastic film is extruded onto the surface of the elastic member facing away from the forming structure. A pneumatic vacuum is applied to the thermoplastic film and the elastic member so that the thermoplastic film is simultaneously apertured and bonded to the elastic member thereby forming a breathable composite elastic material.

FIELD OF THE INVENTION

The present invention relates to a method for forming a compositeelastic material suitable for use in disposable absorbent articles suchas disposable diapers, incontinence briefs, training pants, femininehygiene garments, and the like.

As used herein, the term "composite elastic material" refers to amultilayer or multicomponent material adapted to stretch and recover andwhich has at least one elastic member, layer or component, such as anelastic scrim, joined to another member, layer or component such as athermoplastic film.

BACKGROUND OF THE INVENTION

Infants and other incontinent individuals wear disposable absorbentarticles such as diapers to receive and contain urine and other bodyexudates. Absorbent articles function both to contain the dischargematerials and to isolate these materials from the body of the wearer andfrom the wearer's garments and bed clothing. Disposable absorbentarticles having many different basic designs are known to the art.

However, absorbent articles have a tendency to sag or gap away from andto slide/slip down on the body of the wearer during wear. Thissagging/gapping and sliding/slipping is caused by the relative motionsof the wearer as the wearer breathes, moves, and changes positions bythe downward forces generated when the absorbent article is loaded withbody exudates, and by the deformation of the materials of the absorbentarticle itself when subjected to such wearer's motions. Thissagging/gapping and sliding/slipping of the absorbent article can leadto premature leakage and poor fit of the absorbent article about thewearer in the waist regions and the leg regions of the absorbentarticle.

In order to more snugly fit absorbent articles about the wearer, certaincommercially available absorbent articles have been provided withelasticized waistbands and elasticized side panels. An example of adisposable diaper with elasticized waistbands and elasticized sidepanels is disclosed in U.S. Pat. No. 5,152,092 issued to Buell et al. onSep.29, 1992. The elasticized waistband and the elasticized side panelstypically comprise an elastic member affixed between portions of theabsorbent article, for example, between the topsheet and the backsheet.The elasticized waistband and the elasticized side panels are thus,designed to expand and contract with the wearer's motions to maintainthe fit of the absorbent article about the wearer during use.

The incorporation of elastic members into disposable absorbent productssuch as disposable diapers has increased both the cost of materials andconstruction of the disposable diapers. In addition, it has been foundthat absorbent articles having elasticized waistbands and elasticizedside panels comprising elastomeric films can make the absorbent articlefeel hot and uncomfortable to wear because the elastomeric film isimpermeable to air and/or moisture thereby making the absorbent articlefeel hot and uncomfortable in the waist region and in the side panels.

Therefore, it is an object of the present invention to provide a methodfor forming a composite elastic material which is breathable.

It is another object of the present invention to provide a method forforming a breathable composite elastic material which is suitable foruse in a disposable absorbent article.

It is a further object of the present invention to provide a low costmethod for forming a composite elastic material.

These and other objectives of the present invention will be more readilyapparent when considered in reference to the following description andwhen taken in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

The present invention provides a method for forming a composite elasticmaterial. An elastic member comprising at least one elastic strand isfed onto a rotating forming structure exhibiting a multiplicity ofapertures therein. The elastic member has a surface facing the formingstructure and another surface facing away from the forming structure. Athermoplastic film is extruded onto the surface of the elastic memberfacing away from the forming structure and onto the forming structureitself. A pneumatic vacuum is applied to the thermoplastic film and theelastic member so that the thermoplastic film is simultaneouslyapertured and bonded to the elastic member thereby forming a breathablecomposite elastic material.

The elastic member preferably comprises a plurality of longitudinalstrands and a plurality of transverse strands interconnected to oneanother. In a preferred embodiment all of the longitudinal andtransverse strands are comprised of an elastic material. Alternatively,only the longitudinal strands or only the transverse strands arecomprised of an elastic material depending on the desired direction ofstretch of the composite elastic material. The other strands which arenot elastic are preferably comprised of a thermoplastic material.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing outand distinctly claiming the subject matter which is regarded as thepresent invention, it is believed that the invention will be betterunderstood from the following description which is taken in conjunctionwith the accompanying drawings, in which:

FIG. 1 is a plan view of an absorbent article comprising the compositeelastic material formed according to the method of the present inventionin the elasticized waistband and in the elasticized side panels;

FIG. 2 is a simplified side elevation view showing a method for formingthe composite elastic material of the present invention;

FIG. 3 is an enlarged fragmentary perspective illustration of a formingstructure of the present invention;

FIG. 4 is an enlarged fragmentary perspective illustration of apreferred elastic member of the present invention;

FIG. 5 is an enlarged fragmentary perspective illustration of acomposite elastic material formed according to the method of the presentinvention;

FIG. 6 is a simplified perspective view showing another method forforming a composite elastic material of the present invention; and

FIG. 7 is a simplified perspective view showing another method forforming a composite elastic material of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term "absorbent article" refers to devices whichabsorb and contain body exudates, and, more specifically, refers todevices which are placed against the skin of the wearer to absorb andcontain the various exudates discharged from the body. The term"disposable" is used herein to describe absorbent articles which are notintended to be laundered or otherwise restored or reused as an absorbentarticle after a single use, (i.e., they are intended to be discarded andpreferably, recycled, composted or otherwise disposed of in anenvironmentally compatible manner). A "unitary" absorbent article refersto an absorbent article which is formed of separate parts unitedtogether to form a coordinated entity so that they do not requireseparate manipulative parts like a separate holder and liner.

A preferred embodiment of a unitary absorbent article comprising anelasticized waistband and elasticized side panels each comprising thecomposite elastic material formed by the method of the present inventionis the disposable absorbent article, disposable diaper 20, shown inFIG. 1. As used herein, the term "diaper" refers to an absorbent articlegenerally worn by infants and incontinent persons that is generally wornabout the lower torso of the wearer. It should be understood, however,that the present invention is also applicable to other absorbentarticles such as incontinence briefs, diaper holders, feminine hygienegarments, training pants, and the like.

With reference to FIG. 1, an absorbent article, such as diaper 20,generally comprises a topsheet 22, a backsheet 24 joined to the topsheet22, and an absorbent core 26 positioned between the topsheet 22 and thebacksheet 24. The diaper 20 preferably further comprises elasticized legcuffs 28, elasticized side panels 30, an elasticized waistband 32 and afastening system 34.

The diaper 20 is shown in FIG. 1 to have an outer surface 42 (facing theviewer in FIG. 1), an inner surface 44 opposed to the outer surface 42,a front waist region 36, a rear waist region 38 opposed to the frontwaist region 36, a crotch region 39 positioned between the front waistregion 36 and the rear waist region 38, and a periphery which is definedby the outer perimeter or edges of the diaper in which the longitudinaledges are designated 46 and the end edges are designated 48. The innersurface 44 of the diaper 20 comprises that portion of the diaper 20which is positioned adjacent to the wearer's body during use (i.e., theinner surface 44 generally is formed by at least a portion of thetopsheet 22 and other components joined to the topsheet 22). The outersurface 42 comprises that portion of the diaper 20 which is positionedaway from the wearer's body (i.e., the outer surface 42 is generallyformed by at least a portion of the backsheet 24 and other componentsjoined to the backsheet 24). As used herein, the term "joined"encompasses configurations whereby an element is directly secured to theother element by affixing the element directly to the other element inconfigurations whereby the element is indirectly secured to the otherelement by affixing the element to intermediate member(s) which in turnare affixed to the other element. FIG. 1 shows a preferred embodiment ofthe diaper 20 in which the topsheet 22 and the backsheet 24 have lengthand width dimensions generally larger than those of the absorbent core26. The topsheet 22 and the backsheet 24 extend beyond the edges of theabsorbent core 26 to thereby form the periphery of the diaper 20.

The absorbent core 26 may be any absorbent means which is generallycompressible, conformable, non-irritating to the wearer's skin, andcapable of absorbing and containing liquids such as urine and other bodyexudates. As shown in FIG. 1, the absorbent core 26 has a garmentsurface, a body surface, side edges, and waist edges. The absorbent coremay be manufactured in a wide variety of sizes and shapes and form awide variety of liquid-absorbent materials commonly used in disposablediapers and other absorbent articles such as comminuted wood pulp, whichis generally referred to as airfelt. Examples of other suitableabsorbent materials include creped cellulose wadding; meltblown polymersincluding colorer; chemically stiffened, modified, or cross-linkedcellulosic fibers; tissue including tissue wraps and tissue laminates;absorbent foams; absorbent sponges; superabsorbent polymers; absorbentgelling material; or any equivalent material or combinations ofmaterials. The configuration and construction of the absorbent core mayalso be varied (e.g., the absorbent core may have varying caliper zones,a hydrophilic gradient, a superabsorbent gradient, or a lower averagedensity and lower average basis weight acquisition zones; or maycomprise one or more layers or substrates). The total absorbent capacityof the absorbent core, should, however, be compatible with the designloading and the intended use of the diaper 20. Further, the size andabsorbent capacity of the absorbent core may be varied to accommodatewearers ranging from infants through adults.

The backsheet 24 is preferably impervious to liquids (e.g., urine) andis preferably manufactured from a flexible material. As used herein, theterm "flexible" refers to materials which are compliant and will readilyconform to the general shape and contours of the human body. Thebacksheet prevents the exudates absorbed and contained in the absorbentcore from wetting articles which contact the diaper 20 such as bedsheets and undergarments. The backsheet may thus comprise a woven ornonwoven material, polymeric films such as thermoplastic films ofpolyethylene or polypropylene, or composite material such as afilm-coated nonwoven material. Preferably, the backsheet is athermoplastic film having a thickness of from about 0.012 mm (0.5 mil)to about 0.051 mm (2.0 mils). The backsheet is preferably embossedand/or matte finished to provide a more clothlike appearance. Further,the backsheet may permit vapors to escape from the absorbent core (i.e.,breathable) while still preventing exudates from passing through thebacksheet.

The topsheet 22 is compliant, soft feeling and non-irritating to thewearer's skin. Further, the topsheet is liquid pervious permittingliquids (e.g., urine) to readily penetrate through its thickness. Asuitable topsheet may be manufactured from a wide range of materials,such as porous foams; reticulated foams; apertured plastic films; orwoven or nonwoven webs of natural fibers (e.g., wood or cotton fibers),synthetic fibers (e.g., polyester or polypropylene fibers), or acombination of natural and synthetic fibers. Preferably, the topsheet ismade of a hydrophobic material to isolate the wearer's skin from theliquids contained in the absorbent core. There are a number ofmanufacturing techniques which may be used to manufacture the topsheet.For example, the topsheet may be a nonwoven web of fibers, spunbonded,carded, wet-laid, meltblown, hydroentangled, combinations of the aboveor the like. A preferred topsheet comprises a carded nonwoven web ofsynthetic fibers.

The elasticized waistband 32 preferably comprises a portion of thetopsheet 22, a portion of the backsheet 24 and a composite elasticmaterial 60 positioned between the topsheet 22 and the backsheet 24. Theelasticized side panel 30 preferably comprises a portion of the topsheet22, a portion of the backsheet 24 and a composite elastic material 60positioned between the topsheet 22 and the backsheet 24.

The composite elastic material 60 is preferably joined to the topsheet22 and the backsheet 24 by attachment means such as those well known inthe art. For example, the composite elastic material 60 may be securedto the topsheet 22 and/or the backsheet 24 by a continuous layer ofadhesive, a patterned layer of adhesive, or an array of separate lines,spirals or spots of adhesive. The attachment means will preferablycomprise an open pattern network of filaments of adhesive as isdisclosed in U.S. Pat. No. 4,573,986 issued to Minetola and Tucker onMar. 4, 1986, and which is incorporated herein by reference. Anexemplary attachment means of an open pattern network of filamentscomprises several lines of adhesive filaments swirled into a spiralpattern such as illustrated by the apparatus and methods shown in U.S.Pat. No. 3,911,173 issued to Sprague, Jr. on Oct. 7, 1975; U.S. Pat. No.4,785,996 issued to Ziecker, et al. on Nov. 22, 1978; and U.S. Pat. No.4,842,666 issued to Werenicz on Jun. 27, 1989. Each of these patents areincorporated herein by reference. Alternatively, the attachment meansmay comprise heat bonds, pressure bonds, ultrasonic bonds, dynamicmechanical bonds, or any other suitable attachment means or combinationsof these attachment means as are known in the art.

A particularly preferred process for forming the composite elasticmaterial of the present invention is illustrated in FIG. 2. In theembodiment shown in FIG. 2, an elastic member 100 comprising at leastone elastic strand, preferably a plurality of elastic strands is fedfrom a supply roll 102 onto the surface of a forming drum 118 aboutwhich a forming structure 115 continuously rotates at substantially thesame speed as the incoming elastic member. The forming drum 118preferably includes an internally located vacuum chamber 120 which ispreferably stationary relative to the moving forming structure 115.

Referring now to FIG. 3 there is shown a greatly enlarged fragmentarysegment of forming structure 115. Forming structure 115 includes aplurality of apertures 116. The forming structure 115 exhibits afiber-like cross-section of a type generally disclosed in commonlyassigned U.S. Pat. No. 4,342,314 issued to Radel et al. on Aug. 3, 1982,which patent is hereby incorporated herein by reference. The formingstructure 115 may have various aperture sizes, aperture shapes, andaperture densities. The aperture spacing may be in a regular pattern orit may vary randomly, as desired. Examples of other suitable formingstructures are disclosed in commonly assigned U.S. Pat. No. 4,609,518issued to Curro et al. on Sep. 2, 1986, which patent is herebyincorporated herein by reference.

Referring again to FIG. 2 as the elastic member 100 is fed onto theforming drum 118 about which forming structure 115 continuously rotates,one surface 103 of elastic member 100 faces the forming structure 115and directly contacts the forming structure 115 while the other surface104 of elastic member 100 faces away from the forming structure 115. Asthe forming structure 115 rotates, a thermoplastic film 130 is extrudedfrom extruder 132 directly onto the surface 104 of the elastic member100 facing away from forming structure 115. The vacuum chamber 120subjects the elastic member 100 and the thermoplastic 130 film to apneumatic vacuum. The pneumatic vacuum sucks portions of thethermoplastic film into the apertures 116 of the forming structure 115thereby forming apertures in the thermoplastic film. In addition, thevacuum pulls the thermoplastic film against the elastic member therebybonding the thermoplastic film to the elastic member to form abreathable composite elastic material 160. The composite elasticmaterial 160 is then removed from the surface of the forming structure115 about an idler roll 170 and is taken up on wind up roll 172.

Referring now to FIG. 4 there is shown an enlarged fragmentedperspective illustration of a preferred elastic member, elastic scrim100. As seen in FIG. 4, the elastic scrim 100 comprises a plurality ofelastic strands 105 extending in a first or longitudinal direction and aplurality of elastic strands 106 extending in a second or transversedirection perpendicular to the first direction. The longitudinal strands105 and the transverse strands 106 are interconnected to one another.The elastic scrim 100 has a plurality of openings or apertures 107distributed therein to produce a net-like construction. The elasticstrands 105 and 106 are shown in FIG. 4 to be oriented to produceopenings 107 having a generally square configuration. However, elasticstrands 105 and 106 may be arranged to produce openings of otherconfigurations such as rectangular, diamond, etc. The elastic scrim 100of the present invention need not have the symmetrical, regular array ofapertures of a reticulated member, but may merely include a plurality ofinterconnected elastic elements defining apertures therebetween.Depending on the properties of the elastic material including themodulus of elasticity and the thickness and width of the elastic strands105 and 106, the number of openings 107 may vary from 2 to 100 openingsper linear inch in both the longitudinal and transverse direction of theelastic member 100. In addition, the elastic strands 105 and 106 may beof different widths in the longitudinal or transverse direction, and thespacing between the elements may vary from the transverse to thelongitudinal direction. The thickness of the elastic scrim 100 ispreferably from about 1 mil to about 50 mils and more preferably fromabout 5 mils to about 20 mils.

Examples of suitable elastic scrims are disclosed in U.S. Pat. No.4,062,995 issued to Korpman on Dec. 13, 1977; and in U.S. Pat. No.4,573,991 issued to Pieniak et al. on Mar. 4, 1986.

Examples of suitable materials for use as the elastic strands 105 and106 include but are not limited to elastomeric foams, "live" syntheticor natural rubber, and lycra. In some embodiments it may be necessaryfor both elastic strands 105 and 106 to be elastic. This is true whereit is desirable to provide stretch in multiple directions. However, inother embodiments, it may be necessary for only one of the strands,either one of strands 105 or 106 to be elastic. This is true where it isdesirable to provide stretch in only one direction. In those situationswhere it is desirable to provide stretch in only one direction, at leastone of the elastic strands, for example elastic strand 105, need beelastic. The other elastic strand, for example elastic strand 106, maybe made from a wide variety of other materials. Examples of suitablematerials for use as the non-elastic strands 106 include but are notlimited to thermoplastic materials such as polyethylene, polypropylene,and polyester and the like.

Referring now to FIG. 5, there is shown a fragmented perspectiveillustration of the breathable composite elastic material 160. As seenin FIG. 5 the breathable composite elastic material 160 comprises theelastic member 100 comprising interconnected elastic strands 105 and 106bonded to apertured thermoplastic film 130. Apertured film 130 comprisesa plurality of apertures 133 generally corresponding to apertures 116 informing structure 115, as shown in FIG. 3.

The apertures 133 in the apertured film 130 are preferably smaller insize than the openings 107 of the elastic member 100. However, theapertures 133 may be the same size as the openings 107 or larger thanthe openings 107 in the elastic member 100.

The apertures 133 in the composite elastic material 160 allow thecomposite to be breathable permitting the passage and air and vapor.When used as the elastic component of the elasticized waistband and/orthe elasticized side panels, the composite elastic material is both aselastic, breathable, and relatively low cost compared to traditionalelastic materials.

An alternative process for forming a composite elastic material of thepresent invention is illustrated in FIG. 6. In the embodiment shown inFIG. 6, a single elastic strand 200 is fed from a supply source, (notshown for simplicity), onto the surface of a forming drum 218 aboutwhich a forming structure 215 continuously rotates. The forming drum 218includes an internally located vacuum chamber 220 which is preferablystationary relative to the moving forming structure 215. A suitableforming structure is forming structure 115 shown in FIG. 3.

As the elastic strand 200 is fed onto the forming drum 218 about whichthe forming structure 215 continuously rotates, the elastic strand 200is preferably oscillated in a back and forth motion to extend theelastic strand 200 from one edge of the forming structure 215 to theopposite edge of the forming structure 215. While not shown forsimplicity, any suitable means for oscillating the elastic strand 200may be used. As the forming structure 215 rotates, a thermoplastic film230 is extruded from extruder 232 directly onto the surface of theelastic strand 200 facing away from the forming structure 215. Thevacuum chamber 220 subjects the elastic strand and the thermoplasticfilm to a pneumatic vacuum. The pneumatic vacuum sucks portions of thethermoplastic film into the apertures of the forming structure 215thereby forming apertures in the thermoplastic film. In addition, thevacuum pulls the thermoplastic film against the elastic strand 200thereby bonding the thermoplastic film to the elastic strand to form abreathable composite elastic material 260. The breathable compositeelastic material 260 is then removed from the surface of the formingstructure 215 about an idler roll 270 and is preferably taken up on awind up roll, (not shown for simplicity).

In the embodiment of FIG. 6 a single elastic strand is shown.Alternatively, multiple elastic strands may be fed in an oscillatingmanner onto the forming structure 215. For example, two, three, four ormore elastic strands may be fed in an oscillating manner onto theforming structure 215.

Another process for forming a composite elastic material of the presentinvention is illustrated in FIG. 7. In the embodiment shown in FIG. 7,an elastic member 300 comprising a plurality of elastic strands is fedfrom a supply source, (not shown for simplicity), onto the surface of aforming drum 318 about which a forming structure 315 continuouslyrotates. The forming drum 318 includes an internally located vacuumchamber 320 which is stationary relative to the moving forming structure315. A suitable forming structure 315 is forming structure 115 shown inFIG. 3.

The elastic member 300 comprises a plurality of individual elasticstrands preferably spaced apart from one another. In the embodimentshown in FIG. 7, the elastic member 300 comprises seven individualelastic strands. However, any suitable number of individual elasticstrands may be used. Unlike the method shown in FIG. 6, the individualelastic strands of the elastic member 300 in FIG. 7 are not oscillatedin a back and forth motion. Instead, the individual elastic strands ofelastic member 300 are simply fed onto the forming structure 315 from asupply source.

As the forming structure 315 rotates, a thermoplastic film 330 isextruded from extruder 332 directly onto the surface of the elasticmember 300 facing away from the forming structure 315. The vacuumchamber 320 subjects the elastic as member and a thermoplastic film to apneumatic vacuum. The pneumatic vacuum sucks portions of thethermoplastic film into the apertures of the forming structure therebyforming apertures in the thermoplastic film. In addition, the vacuumpulls the thermoplastic film against the elastic member thereby bondingthe thermoplastic film to the elastic member to form a breathablecomposite elastic material 360. The breathable composite elasticmaterial 360 is removed from the surface of the forming structure 315about an idler roll 370 and taken up on a wind up roll (not shown forsimplicity).

While particular embodiments of the present invention have beenillustrated and described, it would be obvious to those skilled in theart that various other changes and modifications can be made withoutdeparting from the spirit and scope of the invention. It is thereforeintended to cover in the appended claims all such changes andmodifications that are within the scope of this invention.

What is claimed is:
 1. A method for forming a composite elasticmaterial, said method comprising the steps of:a) feeding an elasticmember comprising at least one elastic strand onto a rotating formingstructure exhibiting a multiplicity of apertures therein, said elasticmember having a surface facing said forming structure and a surfacefacing away from said forming structure; b) extruding a thermoplasticfilm onto the surface of the elastic member facing away from the formingstructure; and c) applying a pneumatic vacuum to the thermoplastic filmand the elastic member so that the thermoplastic film is simultaneouslyapertured and bonded to the elastic member while still on said formingstructure.
 2. The method of claim 1 wherein said elastic membercomprises an elastic scrim.
 3. The method of claim 1 wherein saidelastic member comprises a plurality of longitudinal strands and aplurality of transverse strands interconnected to one another.
 4. Themethod of claim 3 wherein said longitudinal strands comprise an elasticmaterial.
 5. The method of claim 4 wherein said transverse strandscomprise a thermoplastic material.
 6. The method of claim 3 wherein saidtransverse strands comprise an elastic material.
 7. The method of claim6 wherein said longitudinal strands comprise a thermoplastic material.8. The method of claim 1 wherein said composite elastic material forms aportion of an absorbent article.
 9. The method of claim 8 wherein saidcomposite elastic material forms an elasticized waistband in saidabsorbent article.
 10. The method of claim 8 wherein said compositeelastic material forms an elasticized side panel in said absorbentarticle.
 11. A method for forming a composite elastic material, saidmethod comprising the steps of:a) feeding an elastic member comprisingat least one elastic strand onto a rotating forming structure exhibitinga multiplicity of apertures therein, said elastic member having asurface facing said forming structure and a surface facing away fromsaid forming structure; b) extruding a thermoplastic film onto thesurface of the elastic member facing away from the forming structure;and c) simultaneously aperturing the thermoplastic film and bonding thethermoplastic film to the elastic member while still on said formingstructure.
 12. The method of claim 11 wherein said elastic membercomprises an elastic scrim.
 13. The method of claim 11 wherein saidelastic member comprises a plurality of longitudinal strands and aplurality of transverse strands interconnected to one another.
 14. Themethod of claim 13 wherein said longitudinal strands comprise an elasticmaterial.
 15. The method of claim 14 wherein said transverse strandscomprise a thermoplastic material.
 16. The method of claim 13 whereinsaid transverse strands comprise an elastic material.
 17. The method ofclaim 16 wherein said longitudinal strands comprise a thermoplasticmaterial.
 18. The method of claim 11 wherein said composite elasticmaterial forms a portion of an absorbent article.
 19. The method ofclaim 18 wherein said composite elastic material forms an elasticizedwaistband in said absorbent article.
 20. The method of claim 18 whereinsaid composite elastic material forms an elasticized side panel in saidabsorbent article.